Olefin polymers are used in a wide variety of products, from sheathing for wire and cable to film. Olefin polymers are used, for instance, in injection or compression molding applications, in extruded films or sheeting, as extrusion coatings on paper, for example photographic paper and digital recording paper, and the like. Improvements in catalysts have made it possible to better control polymerization processes, and thus influence the properties of the bulk material. Increasingly, efforts are being made to tune the physical properties of plastics for lightness, strength, resistance to corrosion, permeability, optical properties, and the like, for particular uses. Chain length, polymer branching and functionality have a significant impact on the physical properties of the polymer. Accordingly, novel catalysts are constantly being sought in attempts to obtain a catalytic process for polymerizing olefins which permits more efficient and better controlled polymerization of olefins.
Conventional polyolefins are prepared by a variety of polymerization techniques, including homogeneous liquid phase, gas phase, and slurry polymerization. Certain transition metal catalysts, such as those based on titanium compounds (e.g. TiCl.sub.3 or TiCl.sub.4) in combination with organoaluminum cocatalysts, are used to make linear and linear low density polyethylenes as well as poly-.alpha.-olefins such as polypropylene. These so-called "Ziegler-Natta" catalysts are quite sensitive to oxygen and are ineffective for the copolymerization of nonpolar and polar monomers.
In contrast to the volumes of work describing early metal group 4-6 olefin oligomerization and polymerization catalysts, there have been relatively few reports of group 7-10 catalysts for the polymerization of olefins. WO 96/23010 describes the polymerization of olefins using cationic nickel, palladium, iron, and cobalt complexes containing diimine and bisoxazoline ligands.
WO 96/23010 also describes a series of novel polyolefins based on ethylene homopolymer and copolymers, as well as homo- and copolymers of alpha-olefins including propylene, 1-hexene, and methylacrylate among others. WO 97/02298 further complements WO 96/23010 by describing other possible ligands coordinated to nickel and the use of the corresponding complexes in the polymerization of alkenes. See also, WO 98/47933, WO 98/40420, WO 98/40374, and WO 98/37110.
European Patent Application Serial No. 381,495 describes the polymerization of olefins using palladium and nickel catalysts which contain selected bidentate phosphorous containing ligands.
L. K. Johnson et al., J. Am. Chem. Soc., 1995, 117, 6414, describe the polymerization of olefins such as ethylene, propylene, and 1-hexene using cationic .alpha.-diimine-based nickel and palladium complexes. These catalysts have been described to polymerize ethylene to high molecular weight branched polyethylene. In addition to ethylene, Pd complexes act as catalysts for the polymerization and copolymerization of olefins and methyl acrylate.
G. F. Schmidt et al., J. Am. Chem. Soc. 1985, 107,1443, describe a cobalt(III) cyclopentadienyl catalytic system having the structure [C.sub.5 Me.sub.5 (L*)CoCH.sub.2 CH.sub.2 -.mu.-H].sup.+, which provides for the "living" polymerization of ethylene.
M. Brookhart et al., Macromolecules 1995, 28, 5378, disclose using such "living" catalysts in the synthesis of end-functionalized polyethylene homopolymers.
U. Klabunde, U.S. Pat. Nos. 4,906,754, 4,716,205, 5,030,606, and 5,175,326, describes the conversion of ethylene to polyethylene using anionic phosphorous, oxygen donors ligated to Ni(II). The polymerization reactions were run between 25 and 100.degree. C. with modest yields, producing linear polyethylene having a weight-average molecular weight ranging between 8K and 350 K. In addition, Klabunde describes the preparation of copolymers of ethylene and functional group containing monomers.
M. Peuckert et al., Organomet. 1983, 2(5), 594, disclose the oligomerization of ethylene using phosphine, carboxylate donors ligated to Ni(II), which showed modest catalytic activity (0.14 to 1.83 TO/s). The oligomerizations were carried out at 60 to 95.degree. C. and 10 to 80 bar ethylene in toluene, to produce .alpha.-olefins.
R. E. Murray, U.S. Pat. Nos. 4,689,437 and 4,716,138, describes the oligomerization of ethylene using phosphine, sulfonate donors ligated to Ni(II). These complexes show catalyst activities approximately 15 times greater than those reported with phosphine, carboxylate analogs.
W. Keim et al., Angew. Chem. Int. Ed. Eng. 1981, 20,116, and V. M. Mohring, et al., Angew. Chem. Int. Ed. Eng. 1985, 24,1001, disclose the polymerization of ethylene and the oligomerization of .alpha.-olefins with aminobis(imino)phosphorane nickel catalysts; G. Wilke, Angew. Chem. Int. Ed. Engl. 1988, 27, 185, describes a nickel allyl phosphine complex for the polymerization of ethylene.
K. A. O. Starzewski et al., Angew. Chem. Int. Ed. Engl. 1987, 26, 63, and U.S. Pat. No. 4,691,036, describe a series of bis(ylide) nickel complexes, used to polymerize ethylene to provide high molecular weight linear polyethylene.
WO Patent Application 97/02298 discloses the polymerization of olefins using a variety of neutral N, O, P, or S donor ligands, in combination with a nickel(0) compound and an acid.
Brown et al., WO 97/17380, describes the use of Pd .alpha.-diimine catalysts for the polymerization of olefins including ethylene in the presence of air and moisture.
Fink et al., U.S. Pat. No. 4,724,273, have described the polymerization of .alpha.-olefins using aminobis(imino)phosphorane nickel catalysts and the compositions of the resulting poly(.alpha.-olefins).
Recently Vaughan et al. WO 9748736, Denton et al. WO 9748742, and Sugimura et al. WO 9738024 have described the polymerization of ethylene using silica supported .alpha.-diimine nickel catalysts.
Additional recent developments are described by Sugimura et al., in JP96-84344, JP96-84343, by Yorisue et al., in JP96-70332, by Canich et al. WO 9748735, McLain et al. WO 9803559, Weinberg et al. WO 9803521 and by Matsunaga et al. WO 9748737.
Cobalt(II) and iron(II) complexes with coordinated 2,6-bisiminopyridine ligands were independently reported by Brookhart at the University of North Carolina in collaboration with DuPont (Small, B. L.; Brookhart, M.; Benneth, A. M. A. J. Am. Chem. Soc. 1998, 120, 4049; Small, B. L.; Brookhart, M. J. Am. Chem. Soc. 1998, 120, 7143) and by Gibson at Imperial College in collaboration with BP Chemicals (Britovsek, G. J. P. et al. Chem. Commun. 1998, 849). Upon activation with modified methylaluminoxane, those catalysts polymerize ethylene in good rate. The iron complexes could also polymerize propylene with a number average molecular weight consistently higher than 5000. The polypropylene thus obtained was found to be mainly isotactic. (See also WO 99/02472, 98/27124 and WO 98/30612).
Brookhart and coworkers have also described a cobalt(III) cyclopentadienyl system of the general structure [C.sub.5 Me.sub.5 (L*)CoCH.sub.2 CH.sub.2 -.mu.-H].sup.+ (Schmidt, G. F.; Brookhart, M. J. Am. Chem. Soc. 1985, 107,1443). These catalysts effect the "living" polymerization of ethylene. The living nature of these catalysts has been exploited for the synthesis of end-functionalized polyethylene homopolymers (Brookhart, M.; DeSimone, J. M.; Grant, B. E.; Tanner, M. J. Macromolecules 1995, 28, 5378).
Klabunde and Ittel from DuPont reported the conversion of ethylene to polyethylene using phosphorous/oxygen chelate ligands. The polymerization reactions were run between 25 and 100.degree. C. with modest productivities resulting in linear polyethylene having a weight average molecular weight ranging between 8K and 350K. (Klabunde, U.; Ittel, S. D. J. Mol. Cat. 1987, 41,123-134.)
The polymerization of ethylene and the oligomerization of .alpha.-olefins with aminobis(imino)phosphorane-nickel catalysts have also been described. (Keim, W.; Appel, R.; Storeck, A.; Kruger, C.; Goddard, R. Angew. Chem. Int. Ed. Eng. 1981, 20,116. Mohring, V. M.; Fink, G. Angew. Chem. Int. Ed. Eng. 1985, 24,1001). Other group 10 catalysts known in the art include a nickel allyl phosphine complex described by Wilke (Wilke, G. Angew. Chem. Int. Ed. Engl. 1988, 27, 185), and a series of bis(ylide) nickel complexes which are reported by K. Alexander Ostoja Starzewski to polymerize ethylene to high molecular weight linear polyethylene. (Starzewski, K. A. O.; Witte, J. Angew. Chem. Int. Ed. Engl. 1987, 26, 63.).